1. Field of the Invention
Embodiments of the invention described herein pertain to the field of aerial cable rail systems. More particularly, these embodiments enable the movement of objects within three-dimensional space.
2. Description of the Related Art
An aerial cable rail system is a system based on an elevated cable or rope, along which objects are transported. Existing cable rail systems have relied on large fixed structures and/or complex control systems in order to facilitate the movement of objects. These systems fail to satisfactorily achieve the full spectrum of ease of control, compact storage, ease of transport, speed, load bearing, volume serviced, extensibility, maintainability and platform stability.
In U.S. Pat. No. 4,625,938, an invention is disclosed in which a camera payload can be moved within three-dimensional space. Since the payload of the invention is reliant on four separate lines, if one of them were to break, a dangerous swinging motion could result since there would be no opposing force to slow down the payload. The invention also requires a computer control system in order to calculate the vectors and change in lengths of the supports ropes in order to move the payload between two points. Therefore, the invention does not provide simple X, Y and Z independence for control purposes.
In U.S. Pat, No. 6,566,834, an invention is disclosed in which a payload can be moved and angularly positioned within three-dimensional space. The invention requires a computer control system in order to calculate the change in lengths of the supports ropes in order to move the payload between two points. The invention appears to require power at the platform and locates the winches for the system on the platform, further reducing the payload capacity of the platform. Furthermore, the invention does not provide simple X, Y and Z independence for control purposes and it appears that complex sensing devices must be deployed in order to keep the cables tensioned properly.
In U.S. Pat, No. 5,585,707, an invention is disclosed in which a robot or person can be readily moved within three-dimensional space. The payload is limited and the support structure is small scale. If the structure were to be scaled up, obstacles such as goal posts or light poles would inhibit the motion of the payload through a path between two points defined within the cube, since there are so many wires required to practice the invention. Also, the invention would not appear to allow the Z-axis to vary beneath the cube, and the size of the cube support structure to service a large volume of space would be extremely expensive to build on the scale required.
In U.S. Pat, No. 5,568,189, an invention is disclosed for moving cameras in three-dimensional space. The problems with the ""189 invention become apparent when attempting to enlarge the scale of the system. FIG. 4 clearly shows how the two parallel highline cables sag inward, when the payload is in the middle of the X, Y space. Since the invention does not use strong rails to support the Y-axis rope, the weight bearing of the invention is dependent upon the strength of the building or structure in which it is mounted and the springs in its weight bearing X-axis connectors. The motors for the various axes are mounted up in the rigging, which would require multiple extremely long power cables to traverse the volume of space along with the payload if the invention were modified for outdoor use. The power cables would total over 3 times the length of the longest axis to drive the far X-axis motor, the Y-axis motor and the Z-axis motor. Mounting heavy motors high in the rigging presents a major safety issue given that suspension lines can break. The size of the motors limits the payload that can be carried, and further limits the speed at which the payload can be carried. The invention is also fixed in size, not allowing for modular addition of X travel, or increasing the Y or Z-axis travel without mounting the structure in a bigger studio or building a bigger hanger.
Embodiments of the invention move objects throughout three-dimensional space by using two supporting ropes each of which connects to both opposing sides of the payload. If one rope breaks, the payload gently travels to the middle of the coverage area in a safe manner, maintaining the given displacement in the other unbroken axis. One rope controls the X-axis motion of the platform and is designated the X movement rope. The other rope controls the Y-axis motion of the platform and is designated the Y movement rope. Displacing equal lengths of the X and Y movement ropes allows the Z-axis of the platform to be traversed. There is no need for a complex computer control system since the Z-axis displacement is substantially independent of X and Y axis movement over a coverage area serviced by the platform. In addition, since the ropes are commanded from one point, distantly located motors and electrical cables are not required. Many types of useful devices may then be attached to the platform including devices that require external power or devices that possess their own power and are operated via wireless signals. Triangle and quadrilateral embodiments may be readily constructed without requiring equal distances between any two support structures.
Creating a three axis movement configuration from only two ropes driven from a point distantly located from the payload is non-trivial, but provides advantages of allowing the motors to be large, power cables to be short and located near a large generator and control computer. Maintenance is readily performed in one location. The Z-axis may also contain a pulley arrangement that multiplies the Z-axis travel.
The system is configured to move objects across any axis by using motors mounted at one support point, on or near the ground, to drive the ropes. These motors connect to a generator that can be as large as the application requires in order to achieve the required payload speed. The sheaves employed in the system may contain high speed bearings and are may be configured to capture the rope in order to prevent derailing in order to add a degree of safety to the system. The drive pulleys attached to the motors comprise grooves that grip the rope in order to prevent slippage. Any known means of driving rope may be substituted for grooved pulleys.
For the purposes of this disclosure the use of the word motor signifies a motor connected to a drive pulley or drum winch. This assumption is made for purposes of illustration since it is well known in the art that the motor must drive any of a number of attachments to actually engage rope.
The system can be scaled to any size by employing longer ropes and moving the attachment points. Embodiments may be configured in scalene triangle or convex or concave quadrilateral arrangements where no two sides are required to have the same length.